ABV calculator
Enter your original and final gravity to get the alcohol content of your beer, plus attenuation, calories and carbs. Works in specific gravity and °Plato: switch the unit and your readings convert.
Readings
Measured with a refractometer? Correct the FG for alcohol first.
Only used for calories and carbs.
ABV
5.3%
- Apparent attenuation · Compare with your yeast's attenuation
- 80%
- Real attenuation
- 65%
- ABV, simple formula · (OG − FG) × 131.25, reads low for strong beers
- 5.3%
- ABW (by weight)
- 4.2%
- Your readings in °P
- OG 12.4 °P · FG 2.6 °P
- Nutrition per 12 fl oz
- 165 kcal · 15.2 g carbs
Runs in your browser. Nothing you enter is sent or stored.
How ABV is calculated
During fermentation, yeast turns sugar into alcohol and CO₂. Alcohol is lighter than water and the sugar is gone, so the gravity drops. The size of that drop tells you how much alcohol was made.
The calculator uses the alternate (Balling) formula, which accounts for the density of alcohol and stays accurate for strong beers. The common shortcut multiplies the gravity drop by 131.25; it is shown for comparison and reads low above about 7–8% ABV.
ABV = 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794
ABV = (OG − FG) × 131.25
- OG
- Original gravity (SG) before fermentation
- FG
- Final gravity (SG) after fermentation
Gravity in °Plato is converted to SG first.
Apparent vs. real attenuation
Apparent attenuation is the share of the gravity drop compared with the original gravity. It is called apparent because alcohol makes the hydrometer read lower than the remaining sugar alone would.
Real attenuation corrects for that and is always lower, typically about 80% of the apparent value. Yeast suppliers quote apparent attenuation, so use it to check whether a fermentation has finished.
AA = (OG − FG) / (OG − 1) × 100
| Yeast | Attenuation |
|---|---|
| English ale | 67–75% |
| American ale (US-05 type) | 73–80% |
| Lager (W-34/70 type) | 75–83% |
| German wheat | 72–78% |
| Belgian ale | 75–85% |
| Saison | 85–95% |
Getting accurate OG and FG readings
The result is only as good as your two readings. Small errors add up: 0.002 SG off on each reading moves the ABV by about half a percent.
- Correct hydrometer readings for sample temperature, or cool the sample to your hydrometer's calibration temperature.
- Degas the final gravity sample: CO₂ bubbles lift the hydrometer and make the reading too low.
- Take the final gravity reading when it stays the same for two or three days.
- Using a refractometer? Its final reading needs an alcohol correction before you use it here.
Built into every BrewForge recipe
In BrewForge your recipe predicts original and final gravity from the malt bill, mash schedule and yeast. On brew day you log the real readings, and ABV and attenuation update on their own, including from WiFi hydrometers like the iSpindel, Tilt or RAPT Pill.
- ABV predicted from your recipe before you brew
- Measured ABV from your logged or hydrometer readings
- Checked against BJCP 2021 style ranges
Use this calculator via API
The same calculation is also a free JSON API: no account, no key, one GET request. Handy for scripts, spreadsheets and AI assistants that should use exact brewing math instead of estimating it.
Add units=imperial (or one unit parameter per value) for °F, gallons and pounds. Every answer lists the inputs, the units and the formula it used.
GET https://brewforge.sh/api/public/calc/abv?og=1.050&fg=1.010
FAQ
Questions & answers
Which ABV formula should I use?
BrewForge uses the alternate formula, 76.08 × (OG − FG) / (1.775 − OG) × FG / 0.794, for every beer. For a typical 5–6% beer it is 0.1–0.2% higher than the simple formula (OG − FG) × 131.25 that many recipes and labels use; above about 8% ABV the simple formula reads noticeably low. The calculator shows both.
Why do the two formulas differ for strong beers?
The standard formula assumes a fixed relationship between gravity drop and alcohol. In strong beers the alcohol itself lowers the density noticeably, so the standard formula underestimates. The alternate formula corrects for this.
Can I calculate ABV without an original gravity reading?
Not reliably. You can estimate the original gravity from the recipe and your brewhouse efficiency, but the result is only as good as that estimate. Next time, take a reading before you pitch the yeast.
Can I use refractometer readings?
The original gravity, yes, after converting Brix to gravity. The final gravity, no: alcohol distorts refractometer readings. Use the refractometer calculator to correct the final reading first.
Does bottle conditioning add alcohol?
A little. Priming sugar for normal carbonation adds roughly 0.1–0.3% ABV. Most homebrewers ignore it, but you can add it for a precise label.
Do the math once. BrewForge does it every brew.
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